There's little that a computer offers that is desperately important to a commuter, IMO. That's not to say it's not nice to have one. It is. It's just more a personal preference thing than a necessity.

I have a Sigma wireless that does a bunch of stuff, but mostly I just use the speedometer, odometers, trip timers, and average speed. I'd use the cadence feature if I could get the sensor attached in a usable location.